Dr. John Horner was the guest on a recent episode of the podcast "The Skeptic's Guide to the Universe." It's a really well conducted interview, which you'd expect from the Skeptic's Guide crew. It mainly deals with Horner's recently published paper which proposed that Stygimoloch, and Dracorex are not distinct species, but are younger forms of Pachycephalosaurus.
They touch on Dr. Robert Bakker's contention that this is not the case, and that he is in possession of a genuine juvenile Pachycephalosaurus that does not resemble either Stygimoloch or Dracorex. You can hear a bit of Horner's irritation as he basically dares Bakker to either publish about it or shut his trap. Juicy.